Is the Anatomical Distribution of Accessory Pathways Influenced by Ethnicity?

Aims: The occurrence of most accessory pathways (AP’s) is sporadic. However, few genetic mutations have been associated with accessory pathways, but mostly as part of a complex syndrome, some of which were related to specific ethnicities. We aim to investigate whether ethnicity influences the prevalence and anatomical distribution of sporadic AP’s.

Methods: All electrophysiological (EP) reports of patients who underwent radiofrequency (RF) ablation of AP’s at the Tel-Aviv Medical Center between 1992 and 2014 were retrospectively analyzed.

Results: Seven hundred consecutive patients were evaluated. Of these, 631 (90%) were Jewish and 69 (10%) were of Arab ethnicity. The prevalence of the different locations and ethnic distribution are presented in Table 1. Distribution of left and right free wall AP’s as well as postero, mid and antero septal atrioventricular (AV) pathways was similar between Jewish and Arabs. In contrast, right atriofascicular AP demonstrating antegrade decremental properties (so called “Mahaim fibers”), were significantly more prevalent among Arabs (8 of 69, 11.6% vs. 12 of 631, 1.9%; p=0.0003). Arab subjects represented a significantly higher proportion among patients with Mahaim type AP than among patients with other APs (40% vs. 9% rate of Arab patients, Mahaim vs. other APs). None of the patients with Mahaim fibers were related, and none had structural heart disease.

Conclusions: The prevalence of atriofascicular AP’s (Mahaim fibers) in the Arab population is significantly higher than in the Jewish population. This ethnic difference supports the hypothesis of a genetic basis for the development of sporadic Mahaim fibers. We are currently performing studies to identify genetic mutations associated with Mahaim AP.

Table 1

Abbreviations: LFW: left free wall; RFW: right free wall.